Managing Noise Floor

[Webhiker]

Apologies if this is off topic. I’m just a n00b looking for advice.

The setup:
Live sound reinforcement for coffee house singer/songwiter gigs. CQ-18T connected to a Bose L1 Pro 8 powered speaker via XLR. Vocal mic, acoustic guitar, and PC (for backing tracks) connected to the CQ as close to unity as possible.

With the Bose output level at or below about 50% the system is very quiet when no audio is playing. Increasing the output on the Bose past about 50% introduces a very audible and annoying hiss to the system.

Questions:
To ensure the best signal-to-noise ratio, where should one adjust the overall volume level? At the mixer or at the power amp? Or am I missing something? Maybe the Bose is a POS system? 🙂

Thanks,
Shawn

[Frenchie]

My look like a stupid question but I need to ask first, how is your L1 Pro 8 input set ?

[Webhiker]

Thanks Frenchie,

Input 2
Treble: 12 o’clock
Bass: 12 o’clock
Reverb: Off
Tonematch: Off
System EQ: Speech

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[Frenchie]

All seems to be normal.
Did you also try via input 3 ?
Maybe an issue with the ToneMatch (even on the OFF setting).
I have 2 Polar HK10 PA system and it give great results with the CQ.

[SQuser]

Is it really just normal (“white”) noise or is it more some other buzzing noise?
If the latter, are the L1, the CQ and all electrical devices connected to it connected to the same power socket?
If that is the cause of the noises and it cannot be changed, try connecting some kind of line transformer between the CQ and F1.

[Webhiker]

Thanks Gents,

I believe it’s just regular ol’ white noise, but, in my limited experience, I’ve never heard it get amplified as loudly as this. There’s no way I could have the system cranked above 50% without the audience asking WTF that noise is… :). Maybe it’s normal….

I’ll try Input 3 and see if that changes things.

Thanks for your feedback. Much appreciated!

Shawn

[SQuser]

Using the input 3 as frenchie already recommended will be the right solution.
The manual of your L1 states that inputs 1 and 2 are only for low levels of microphones (so even dynamic) and instruments, and only the input 3 is for line-level audio sources such as mixers.

> where should one adjust the overall volume level? At the mixer or at the power amp?
Set your gains and faders to “normal” levels so that your LR meters read around 0dB max.
Then adjust your L1 until it is “sufficiently loud”.

[Webhiker]

Thanks SQuser,

I’ll pick up an XLR->TRS adapter today. Appreciate your reply to my other question. In the old days (late 70’s) we used to crank the power amps to 10 and pull off the volume knobs so no one would turn them down. Don’t recall having noise floor issues back then, but I may have been too high to notice. 🙂

[musicnorfolk]

Interesting
Found same issue on a friends JBL speakers at rehearsal yesterday, lots of hiss at higher volumes, coupled with a problem over using a Shure58a beta in the room. It definitely looked like a gain issue. I don’t know enough about the specs of the JBL as I too have a Bose S1, but clearly theres a ‘digital’ link. Found similar digital interference / hiss issues with wireless devices.

In chasing down another recording files problem on my CQ20b I noticed that i was recording at 96k and not my usual 48k setup on the night and its got me wondering if there is a link to sample rate as well given the digital nature of devices these days. Just a thought. I can’t recall setting 96k either so maybe a reset or shutdown flipped the setting instead of just clumsy touch screen usage.

David

[Webhiker]

Using a balanced XLR->TRS adapter to connect to the Bose has improved things. The Bose manual indicates the inputs automatically adjust to line level when TRS is connected to any of the combo inputs. I found the overall volume is decreased when using Input 3, but using TRS on Inputs 1 or 2 maintains the volume and has definitely reduced the noise floor to much more usable levels.

[Author]

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